Novel modulation of dendritic cell response against a chronic virus infection

描述（由申请人提供）：慢性感染病毒经常逃避或抑制宿主免疫系统，以避免免疫监视并在宿主中建立持久性。淋巴细胞性脉络丛脑膜炎病毒（LCMV）克隆13 （cl13）株感染其天然宿主小鼠，诱导深刻的免疫抑制并在宿主体内持续长达100天。LCMV cl13感染引起的免疫抑制与刺激病毒特异性T细胞的最有效抗原呈递树突状细胞（DC）反应的损伤有关。因此，LCMV cl13感染可作为研究病毒-免疫系统相互作用和病毒持久性的良好动物模型。鞘氨醇是鞘脂类的一个单位，是一种生物活性脂质介质，调节多种细胞状况，具有治疗自身免疫性疾病的潜力。事实上，鞘氨醇类似物FTY720是一种很有前景的免疫抑制剂，正在进行III期临床试验，用于治疗多发性硬化症，以取代目前的I型IFN （IFN-2）疗法。然而，鞘氨醇在慢性病毒感染时调节宿主免疫反应的机制还有待进一步阐明。初步数据表明，与已知的免疫抑制活性不同，鞘氨醇类似物在LCMV cl13感染时刺激dc的表型和功能。结果表明，鞘氨醇类似物可以逆转慢性病毒对DC反应的抑制，从而扩大抗病毒T细胞。本研究将进一步探索鞘氨醇类似物直接作用于树突状细胞的新的免疫刺激潜力：1)采用鞘氨醇类似物处理的树突状细胞过继性转移实验，进一步评估鞘氨醇类似物介导的树突状细胞对LCMV cl13感染的调节作用。动力学研究将阐明鞘氨醇类似物条件dc对lcmv特异性T细胞形成、活化和病毒清除的影响；2)采用LCMV cl13持续感染小鼠模型，评价鞘氨醇类似物处理的树突状细胞的细胞治疗潜力；3)进一步，我们将通过生化和免疫学分析来研究鞘氨醇类似物在dc上引发的分子下游信号通路。因此，本研究有望发现新的信号通路，这对于提高抗原呈递DC的能力和鞘氨醇类似物在宿主DC对慢性病毒感染的反应中的作用至关重要。因此，这里提出的项目应该有助于开发新的免疫疗法来治疗慢性病毒性疾病。

DESCRIPTION (provided by applicant): Chronically infecting viruses often evade or suppress the host immune system to avoid immunological surveillance and establish persistence in the host. Lymphocytic choriomeningitis virus (LCMV) clone 13 (Cl 13) strain infects the mouse, its natural host, induces profound immune suppression and persists in the host up to 100 days. The immunosuppression caused by LCMV Cl 13 infection is associated with impairment of the most potent antigen-presenting dendritic cell (DC) response in stimulating virus-specific T cells. Thus, LCMV Cl 13 infection serves as an excellent animal model for study of the virus-immune system interaction and viral persistence. The sphingosine is one unit of the sphingolipid group, a bioactive lipid mediator regulating multiple cellular conditions with curative potential for autoimmune diseases. Indeed, the sphingosine analog FTY720 is a promising immunosuppressant that is being tested in phase III clinical trials for the treatment of multiple sclerosis to replace current type I IFN (IFN-2) therapy. However, the sphingosine's mechanism of modulating the host immune response upon chronic virus infection requires further clarification. Preliminary data indicate that, unlike its known immune-suppressive activity, a sphingosine analog stimulates the phenotype and function of DCs upon LCMV Cl 13 infection. The results indicate that sphingosine analogs could reverse chronic viral suppression of the DC response to expand anti-viral T cells. In this proposal, the new immunostimulatory potential of the sphingosine analog directly acting on DCs will be further explored: 1) Adoptive transfer experiments with the sphingosine analog-treated DCs will be employed to further assess the sphingosine analog-mediated regulation of DCs upon LCMV Cl 13 infection. Kinetic study would illuminate the formation and activation of LCMV-specific T cells and viral clearance that are influenced by the sphingosine analog-conditioned DCs; 2) The cytotherapeutic potential of sphingosine analog- treated DCs will be evaluated by using the mouse model of persistent infection with LCMV Cl 13; 3) Further, molecular downstream signaling pathways triggered by the sphingosine analog on DCs will be investigated by evaluating the performance of biochemical and immunological assays. Accordingly, this research is expected to discover novel signaling pathways important for increasing the potency of antigen-presenting DC's capacity and the role of the sphingosine analog in host DC responses to the chronic virus infection. In consequence, the project proposed here should assist in developing novel immuno-therapeutics to remedy chronic viral diseases. PUBLIC HEALTH RELEVANCE: Multiple viruses evade or suppress dendritic cell (DC) responses to establish persistent infections. Recent identification of sphingosine analogs as immune regulators affecting diverse aspects of host immunity prompted us to investigate their role in the DC-mediated host defense and immune responses against a chronic virus infection. Uncovering the mechanisms by which sphingosine analogs stimulate DCs and identifying the analog-triggered intracellular signaling pathways on DCs could provide a basis for the development of novel DC-mediated immunotherapeutic vaccines to conquer persistent viral diseases.